Pupillary size changes during information processing overload

Abstract

Pupillary size changes were investigated during a one-bit and two-bit information processing task. For an information processing task, a random list of the digits two and three and a random list of the digits one, two, three, and four were presented visually on a digital readout by means of a paper tape reader for a one-bit and two-bit task, respectively. The subject's required response was to depress a pushbutton switch corresponding to the digit presented on the digital readout. For both the one-bit and two-bit tasks, pupil diameter increased with an increasing information processing rate, reached a maximum at maximum information processing capacity, and rapidly constricted as maximum information processing capacity was exceeded.